Early stage detection is the most important matter for treating tumors. Conventionally, each tumor has been detected by measuring respective substance in blood, generally called a tumor marker. The tumor marker is defined as “among substances which produce cancer cells or substances which are produced by normal cells in the body by reacting with cancer cells, those in which their inspection by blood, tissues, excrements (urine and feces) and the like serves as a marker for the diagnosis or treatment of cancers”.
However, since most of the tumor markers are also produced in small amounts caused by diseases other than cancers, they sometimes show false positive in the case of chronic inflammation and the like. For example, it is said that since carcinoembryonic antigen (CEA) is produced by the cells of many organs such as the stomach, large intestine, pancreas, lungs and the like, it causes about 20% of false positive. In addition, since there are tumors whose appropriate tumor markers have not been found, it is the current situation that a tumor marker which can cover all tumors is not present.
On the other hand, it is known that when δ-aminolevulinic acid (ALA) or a derivative thereof is administered, the protoporphyrin IX induced is accumulated into the tumor and exerts its effect for intraoperative diagnosis and treatment (Patent References 1 and 2).    Patent Reference 1: JP-A-11-12197    Patent Reference 2: JP-T-11-501914